The present invention relates to an illumination device for simulating neon or similar lighting, an illumination device that uses one or more fluorescent and/or phosphorescent dyes to provide for emission of light in colors that cannot ordinarily be achieved by the use of LEDs alone, including the ability to control and change the color of the emitted light.
Neon lighting, which is produced by the electrical stimulation of the electrons in the low-pressure neon gas-filled glass tube, has been a main stay in advertising and for outlining channel letters and building structures for many years. A characteristic of neon lighting is that the tubing encompassing the gas has an even glow over its entire length irrespective of the viewing angle. This characteristic makes neon lighting adaptable for many advertising applications, including script writing and designs, because the glass tubing can be fabricated into curved and twisted configurations simulating script writing and intricate designs. The even glow of neon lighting being typically devoid of hot spots allows for advertising without visual and unsightly distractions. Thus, any illumination device that is developed to duplicate the effects of neon lighting must also have even light distribution over its length and about its circumference. Equally important, such lighting devices must have a brightness that is at least comparable to neon lighting. Further, since neon lighting is a well-established industry, a competitive lighting device must be lightweight and have superior “handleability” characteristics in order to make inroads into the neon lighting market. Neon lighting is recognized as being fragile in nature. Because of the fragility and heavy weight, primarily due to its supporting infrastructure, neon lighting is expensive to package and ship. Moreover, it is extremely awkward to initially handle, install, and/or replace. Any lighting device that can provide those previously enumerated positive characteristics of neon lighting, while minimizing its size, weight, and handleability shortcomings, will provide for a significant advance in the lighting technology.
The recent introduction of lightweight and breakage resistant point light sources, as exemplified by high-intensity light-emitting diodes (LEDs), have shown great promise to those interested in illumination devices that may simulate neon or similar lighting and have stimulated much effort in that direction. However, the twin attributes of neon lighting, uniformity and brightness, have proven to be difficult obstacles to overcome as such attempts to simulate neon lighting have largely been stymied by the tradeoffs between light distribution to promote the uniformity and brightness.
In an attempt to address some of the shortcomings of neon, commonly assigned U.S. Pat. No. 6,592,238, which is incorporated in its entirety herein by reference, describes an illumination device comprising a profiled rod of material having waveguide properties that preferentially scatters light entering one lateral surface (“light-receiving surface”) so that the resulting light intensity pattern emitted by another lateral surface of the rod (“light-emitting surface”) is elongated along the length of the rod. A light source extends along and is positioned adjacent the light-receiving surface and spaced from the light-emitting surface a distance sufficient to create an elongated light intensity pattern with a major axis along the length of the rod and a minor axis that has a width that covers substantially the entire circumferential width of the light-emitting surface. In a preferred arrangement, the light source is a string of point light sources spaced a distance apart sufficient to permit the mapping of the light emitted by each point light source into the rod so as to create elongated and overlapping light intensity patterns along the light-emitting surface and circumferentially about the surface so that the collective light intensity pattern is perceived as being uniform over the entire light-emitting surface.
One of the essential features of the illumination device described and claimed in U.S. Pat. No. 6,592,238 is the uniformity and intensity of the light emitted by the illumination device. While it is important that the disadvantages of neon lighting be avoided (for example, weight and fragility), an illumination device would have little commercial or practical value if the proper light uniformity and intensity could not be obtained. This objective is achieved primarily through the use of a “leaky” waveguide rod. A “leaky” waveguide is structural member that functions both as an optical waveguide and light scattering member. As a waveguide, it tends to preferentially direct light entering the waveguide, including the light entering a lateral surface thereof, along the axial direction of the waveguide, while as a light scattering member, it urges the light out of an opposite lateral surface of the waveguide. As a result, what is visually perceived is an elongated light pattern being emitted along the light-emitting lateral surface of the waveguide.
Nevertheless, a problem with illumination devices using leaky waveguides and LEDs, as described and claimed in U.S. Pat. No. 6,592,238, is that the available visible color spectrum is limited by the finite availability of LED colors.
Therefore, in commonly assigned and co-pending U.S. patent application Ser. No. 10/455,639 (U.S. Publication No. 2003/0198049), an application which is also incorporated in its entirety by reference, an illumination device is described that uses fluorescent dyes, thus allowing for emission of light in colors that cannot ordinarily be achieved by use of LEDs alone without significant increase in cost or complexity of the illumination device. Specifically, the illumination device is generally comprised of a rod-like member, a housing, and a light source. In one preferred embodiment, the rod-like member is a waveguide that has an external curved lateral surface serving as a light-emitting surface and an interior lateral surface that serves as a light-receiving surface, such that light entering the waveguide from the light source positioned below the light-receiving surface is scattered within the waveguide so as to exit with diffused distribution out of the curved lateral surface. The housing preferably comprises a pair of side walls that define an open-ended channel that extends substantially the length of the waveguide. The housing generally functions to house the light source and associated electrical accessories, and also preferably serves to collect and reflect light.
Although it is contemplated that various types of light sources could be incorporated into the illumination device described in U.S. patent application Ser. No. 10/455,639, a string or strings of contiguously mounted high-intensity light-emitting diodes (LEDs) is a preferred light source. However, since the available visible color spectrum of an illumination device incorporating LEDs as the light source is limited by the finite availability of LED colors, the illumination device is constructed so as to provide for emission of light with a perceived color that is different than that of the LEDs themselves. Specifically, this is accomplished through the incorporation of a light color conversion system into the illumination device, specifically an intermediate light-transmitting medium extending along and positioned adjacent the light source. This intermediate light-transmitting medium is preferably composed of a substantially translucent polyurethane or similar material tinted with a predetermined combination of one or more fluorescent dyes. Because of the position of the intermediate light-transmitting medium adjacent the light source, light emitted from the light source is directed into the intermediate light-transmitting medium and interacts with the fluorescent dyes contained therein. This light is partially absorbed by each of the fluorescent dyes of the intermediate light-transmitting medium, and a lower-energy light is then emitted from each of the fluorescent dyes and into the light-receiving surface of the waveguide. Thus, through selection of appropriate combinations of dyes and varying the density of the dyes within the intermediate light-transmitting medium, colors across the visible spectrum can be produced, colors that are ultimately observed along the light-emitting surface of the waveguide.
Similarly, in commonly assigned and co-pending U.S. patent application Ser. No. 11/025,019, an application which is also incorporated in its entirety by reference, an illumination device is described that includes an intermediate light-transmitting medium that includes one or more phosphorescent dyes, and thus, also provides a color-changing effect.
It is a paramount object of the present invention to provide an illumination device similar to that described in U.S. patent application Ser. No. 10/455,639 and U.S. patent application Ser. No. 11/025,019, but further allowing for increased ability to control and change the color of the emitted light.